Both glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are peptides called incretin. GLP-1 and GIP are secreted from small intestinal L cells and K cells, respectively.
GLP-1 acts via GLP-1 receptors and is known to have a glucose-dependent insulinotropic action and a feeding suppressive action. On the other hand, GIP is known to have a glucose-dependent insulinotropic action via GIP receptors, though an influence of GIP only on feeding is not clear.
Attempts have been made to search for peptides having GLP-1 receptor/GIP receptor coagonist or glucagon receptor/GLP-1 receptor/GIP receptor triagonist activity and modifications thereof and develop these peptides as anti-obesity drugs, therapeutic drugs for diabetes, or therapeutic drugs for neurodegenerative disorders on the basis of the structure of natural glucagon, GIP, or GLP-1 (Patent Literatures 1 to 50, Non-Patent Literatures 1 and 2). However, the peptide compound and the compound having a selective activating action on GIP receptors of the present invention are not disclosed.